Baling apparatus for forming large bales of crop or other fibrous materials are well known today. Although balers of many designs have been in use for a number of years, mobile balers which produce large round or rectangular bales are a relatively recent development. A typical mobile baler operates continuously, gathering balable material that lies in a windrow on the surface of a field, compacting the material into a bale within a bale chamber and tying and discharging the completed bale in the field.
A primary concern of the designer of a baler mechanism is the expense of shipping and storing completed bales. In order to minimize the amount of space required to store completed bales, it is highly desirable that the bale have a high density in pounds of material per cubic foot. In addition, because round bales tend to roll and are more difficult to handle and store than rectangular bales, rectangular bales are generally preferred over round bales.
It is believed that the even distribution of material in each layer of the bale has an important effect on bale density. One of the advantages found in round balers is that they add layers of material simply by "rolling up" material from the field without disturbing the windrow. In addition, each new layer of material in a round bale is evenly compressed. As a result of this gentle handling and uniform compression, the layers of material in round bales is of relatively even distribution. In contrast, many typical rectangular balers tear sections of material from the incoming windrow and compress the sections into the bale chamber using a horizontal ram. This can result in a relatively uneven distribution of material in each layer of the bale. Therefore, round balers tend to produce higher density bales than typical rectangular balers per unit of compressive force applied.
Prior attempts to overcome these disadvantages have not been entirely successful. For example, in one approach to rectangular baling, the windrow is gathered into a reciprocating chute or conveyor forming bales with layers having a zig-zag pattern. Such a baling apparatus is described in U.S. Pat. No. 4,803,832 to Crawford. Alternatively, the gathered windrow can be transported vertically into an oscillating bale chamber as in U.S. Pat. No. 4,302,923 to Molitorisz. Although these designs improve material distribution in each layer of the bale, bale density is not greatly improved because compressive force is not uniformly applied to each layer. In these designs, a relatively small diameter compression roller traverses each new layer of material as it is added to the bale. It is believed that because only a relatively small area of each layer is subject to high compressive forces at any one time, the area not being compressed may "rebound" resulting in a loss of compression and a decrease in bale density. Moreover, such "roller packing" is conducive to leaf shattering and the resultant loss of protein of the baling material.
Therefore, a need exists for a baler and baling method that is capable of forming large rectangular bales having a high bale density while minimizing leaf shattering and protein loss. A need also exists for a rectangular baler that can produce high density bales having minimum power requirements that is relatively simple in design and operation.